1. Field of the Invention
The present invention relates to organic electroluminescent devices and methods for manufacturing the same, and more particularly, to organic electroluminescent device having an encapsulation film which can prevent the device from deteriorating and can prolong the life time of the device, and methods for manufacturing the same.
2. Background of the Invention
Organic electroluminescent devices have many advantages including high emission efficiency, wide viewing angle, and fast response speed. However, when reacting with moisture and oxygen in the air, an organic electroluminescent device may slowly deteriorate, resulting in shortened lifetime of the device. Also, electrodes of an organic electroluminescent device may often deteriorate due to oxidation.
To overcome such instability, various methods have been proposed, including, for example, vapor deposition and encapsulation of an organic material or inorganic material, encapsulation of a siloxane-based polymer on an organic electroluminescent device by spin coating or molding, coating paraffin on an organic electroluminescent device by dipping, compounding a polymer film having low transparency of oxygen and moisture and encapsulating the same around an organic electroluminescent device, coating shield glass on a device and filling silicon oil between the device and shield glass in order to shield the device from moisture and oxygen, and the like.
In particular, in order to shield an organic electroluminescent device using a polymer from oxygen and moisture, one of the most widely known encapsulation methods is to use vacuum deposition equipment. For example, known methods include encapsulation of a polymer film by depositing a liquid or solid monomer and polymerizing the same, encapsulation using inorganic material deposition to form an inorganic film, encapsulation using both an organic material and an inorganic material, and the like. Also, John D. Affinito et al., Battelle Memorial Institute, proposed that an organic/inorganic composite layer was formed by vacuum deposition to be employed as an encapsulation film of an organic electroluminescent device (U.S. Pat. Nos. 6,268,695, 6,224,948, 6,207,239, 6,228,436, 5,902,641, 6,217,947, 6,203,854, 5,547,508 and 5,395,644. Also, similar organic/inorganic composite layers formed by vacuum deposition were proposed by Eliav Haskal, International Business Machine (U.S. Pat. No. 5,952,778), James R. Sheats, Agilent Technologies Inc. (U.S. Pat. No. 6,146,225) and so on. These techniques had several advantages in that an encapsulation film having a thickness of 3 μm or less could be formed, very low transmission to moisture and oxygen could be achieved, and in-line processing could be realized. However, these techniques require expensive vacuum equipment, complicated processing, and an extended processing time and an increased cost compared to encapsulation of the conventional organic electroluminescent device using a metal cap, resulting in various limitations from the viewpoint of actual manufacture applications.
Also, Hans Biebuyck, et al., International Business Machine, proposed encapsulation by spin coating or molding a siloxane-based polymer, as disclosed in U.S. Pat. Nos. 5,855,994 and 5,734,225, which is advantageous in that a siloxane polymer can be used in a state in which it directly contacts an organic light emitting layer. However, the siloxane-based polymer has relatively high transmission to moisture and oxygen, and is prone to deterioration of an organic electroluminescent device during encapsulation, compared to other polymers. Also, the siloxane-based polymer has poor adhesion to an organic material or inorganic material.
In addition, there have been proposed an encapsulation method using heat reactivity, an encapsulation method using a solvent and so on. In the former method, since an organic electroluminescent device is sensitive to heat, the organic electroluminescent device may unavoidably deteriorate due to heat at a predetermined temperature or higher. Also, in the latter method, a solvent permeates into a light-emitting layer, deteriorating an organic electroluminescent device.